Error detection and correction codes are widely used in communication and storage systems to provide reliable information transmission and recovery. Communication systems can be susceptible to errors in the form of signal degradation which results in distortion or noise in transmitted signals. Signal degradation can also result in a loss of transmitted information. Systems which are susceptible to signal degradation or information loss include wireless or mobile communications systems such as cellular telephone, microwave systems, satellite communications systems, digital television and high speed communications systems such as those that utilize an xDSL communication standard.
Memory storage systems can also be susceptible to errors which result in a loss of stored information. The errors can occur from reliability degradation which causes physical failures within individual memory storage devices. Failure mechanisms which can result from reliability degradation include time dependent dielectric breakdown and electromigration, both common in complementary metal oxide semiconductor (CMOS) integrated circuits.
A number of error correction techniques exist which can be used to detect and correct errors in information, or counteract the effects of signal degradation. The error correction techniques typically use additional amounts of information which can be added to the original stored or transmitted information. The additional information is generated from an error correction code, and is used to check the validity of the original information. The most common types of error correction codes are convolutional (tree) codes and block codes. With these codes, the information is separated into blocks, and each block is encoded into a larger block of data.
Error correction codes can have varying abilities to detect and correct errors. Stronger error detection and correction codes, for example, will allow information to be transmitted and received with lower error rates. These stronger error correction codes usually require more powerful processors or controllers to execute the codes and transmit or store the additional error correction code bits.
The strength of the error correction code is typically chosen for a particular system or application. Once a particular error correction code is chosen for the system or application, the associated execution time or latency time is fixed. In other words, if a higher degree of reliability is required, and high latency error correction routines are used, the system or application will always have the same throughput, even if the reliability requirements are later reduced.